Question 1

What is an Activity in Android?

Accepted Answer

An Activity represents a single screen in an Android application. It's a fundamental component that manages the user interface and interactions. It must be declared in the AndroidManifest.xml to be used.

Question 2

What is the difference between View and ViewGroup?

Accepted Answer

View is the base class for all UI components (Button, TextView, ImageView, etc.). ViewGroup is a subclass of View that contains other Views (or ViewGroups). ViewGroups are layout containers: LinearLayout, RelativeLayout, ConstraintLayout, FrameLayout, etc.

Question 3

What is the correct lifecycle order of an Activity when starting?

Accepted Answer

An Activity's lifecycle starts with onCreate() (initialization and view creation), followed by onStart() (Activity becomes visible but not yet interactive), then onResume() (Activity in foreground and interactive). This sequence is always the same for each Activity start.

Question 4

What is Jetpack's Navigation Component?

Accepted Answer

Navigation Component is a Jetpack library that simplifies navigation between destinations (fragments/activities). It offers automatic back stack management, SafeArgs for type-safe arguments, navigation graph visualization, and handles deep links. It's Google's recommended solution for navigation in modern Android apps.

Question 5

What is Room in Android?

Accepted Answer

Room is a persistence library that provides an abstraction layer over SQLite. It simplifies database access with annotations and generates code to avoid boilerplate. Room is part of Android Jetpack.

Question 6

What is a Service in Android?

Accepted Answer

A Service is an Android component that runs in the background without a user interface. It allows performing long-running operations like downloading files or playing music. It must be declared in the Manifest.

Question 7

What is Jetpack Compose?

Accepted Answer

Jetpack Compose is Google's modern toolkit for building native Android UI declaratively. It simplifies and accelerates UI development using Kotlin. Compose is progressively replacing traditional XML Views.

Question 8

What are the 3 main layers of Clean Architecture?

Accepted Answer

Clean Architecture consists of 3 layers: Presentation (UI, ViewModels), Domain (Use Cases, business entities), and Data (repositories, data sources). Each layer has its responsibility and depends only on inner layers.

Question 9

How to create a Custom Layout in Compose?

Accepted Answer

Use the Layout { measurables, constraints -> } function. It allows measuring children with measurables.forEach { it.measure(constraints) }, then placing them with layout(width, height) { placeables.forEach { it.place(x, y) } }.

Question 10

What is Android Profiler and what are its 4 modules?

Accepted Answer

Android Profiler is a tool integrated into Android Studio that analyzes your app's real-time performance. It helps detect CPU, memory, network, and battery issues to optimize your app. Its 4 modules are: CPU Profiler (CPU usage and call traces), Memory Profiler (heap and allocations tracking), Network Profiler (network requests and bandwidth usage), and Energy Profiler (battery consumption and wake locks).

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Androidの全トピックを探索

Android Fundamentals

Android UI and Resources

Android Lifecycle

Android Navigation

Android Data Management

Android Networking

Android Testing

Android Gradle

Kotlin Language Essentials for Android

Room Database

Background Work

Jetpack Compose

Permissions and Device Features

Firebase for Android

Android MVVM Architecture

Advanced Android Networking

Kotlin Collections and Operators

Kotlin Coroutines and Flow

Android Dependency Injection

Android MVI Architecture

Android Clean Architecture

Android Compose Advanced

Android Performance and Monitoring

Android Security and Privacy

Android CI/CD and Release

Android UX and Form Factors

Android Testing Advanced

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